This invention relates to the field of gas engines, specifically to methods and apparatuses for supplying natural gas to natural gas engines in environments characterized by low temperatures.
Natural Gas Reciprocating Engines are a common site in the oil field. With the easily accessible fuel source of natural gas it becomes quick and easy to convert that gas source to engine horsepower. Applications range from gas compressors, to power generation to pumps . . . and more. Natural Gas Engines will continue to be a major and increasing source of driver horsepower in the oil and gas industry. There are many engines manufactured in the 40's and 50's still in operation today.
Technical improvements over the years have provided smaller/higher horsepower engines. In the past a 5000 hp unit was available only in large bore—low speed engines. A typical engine of this horsepower would be around 40 feet long 8 feet wide and required a major construction project to install. Once installed the engine had to remain right where it was because of the cost to remove it. Today the same or greater horsepower engine is available in a much smaller and more portable package. The move to the conversion of diesel engines to natural gas engines constitutes most of the innovative technology today. The older low speed engines mentioned above were actually conversions of diesels themselves but were extensively re-engineered.
Natural gas engines typically rely on a steady flow of natural gas for efficient and continued operation. The gas supply typically must be reduced from wellhead pressure to an engine-usable pressure of just a few ounces. Further, gas supply direct from the wellhead typically comprises hydrocarbons and hydrates, and, in low temperatures, is subject to condensation, which can interrupt operation of the engine. Further, the pressure differentials across the pressure regulator (often, two separate regulators) can encourage condensation. FIG. 1 is a schematic illustration of current gas supply systems. A wellhead natural gas source supplies gas 111 to a first pressure regulator P1. The first pressure regulator P1 supplied a regulated pressure 112 to a second pressure regulator P2. The second pressure regulator P2 supplies an ounce-level pressure 114 of natural gas to a gas engine E. Exhaust from the engine E is typically exhausted into the surrounding air. In low temperatures, condensation anywhere in the system can interrupt operation of the engine. The gas supply is especially prone to condensation at the pressure regulators P1, P2. There is a need for methods and apparatuses for supplying gas to gas engines that reduce the likelihood of condensation and the consequent interruption of operation of the engine.